Date of Award

2022

Degree Type

Thesis

Department

Ocean Engineering

First Advisor

Chris Baxter

Abstract

Geoacoustic analysis is necessary to characterize the soil profile of a site for a variety of applications, such as earthquake site response or soil-structure interaction analysis. The objectives of this thesis were to: 1.) measure Scholte waves using a fiber optic DAS cable deployed in the seabed and calculate a dispersion curve, and 2.) compare dispersion curves produced from a fiber optic DAS cable and geophone array deployed on land. A dock test was performed by creating an underwater impulse signal near an underwater DAS cable. A valid dispersion curve was not produced because the gauge length was too large (6.38 m). Two additional field tests were performed on land comparing a fiber optic DAS cable and geophone array deployed side by side. In the first test, a comparable dispersion curve was produced using the cylindrical-FDBF technique on both data sets. The fundamental mode was present in both dispersion curves (DAS and geophone array) in the same frequency/phase velocity range. The second test also utilized a fiber optic DAS cable and geophone array, however the DAS cable data was not able to be resolved. Dispersion curves were produced from the geophone array data for each source offset: -5, -10, -15, and -20 m. The fundamental mode was present in all dispersion curves. Inversions were performed for the land-based tests, and the resulting shear wave profile compared with direct measurements from a seismic cone penetration test.

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